Cain, who's in his first year of arbitration eligibility, was offered $2 million after hitting .301/.339/.412 with five home runs, 53 RBI and 28 stolen bases in 471 at-bats in 2014. Herrera, who's also in his first year of arbitration eligibility, was offered $1.15 million after posting a 1.41 ERA and 59:26 K:BB ratio in 70 innings in 2014.

The Royals have been receiving calls regarding the availability of reliever Kelvin Herrera, Jayson Stark of ESPN reports.

Although the Royals are telling teams they prefer not to break up their bullpen, the shortage of free agent bats are forcing Kansas City to at least listen to offers this offseason. According to Stark, one rival executive views Herrera as a "potential closer."

Herrera, 24, spent his first four seasons in the majors with the Royals, registering a 2.56 ERA and a 1.17 WHIP over 214 2/3 innings of relief.

Royals pitcher Kelvin Herrera left Thursday's game early due to an injury.

Herrera entered in the bottom of the seventh inning, and walked the only batter he faced. A trainer came out to the mound following the at-bat, and Herrera was removed. The did not record an out during his appearance. Herrera was taken out with a right forearm injury.